The Zika virus, which is linked to a rare birth defect and other illnesses, is now a big concern in many countries across the Western Hemisphere.

The mosquito-borne disease has spread to 24 countries in Central and South America, Mexico, the Caribbean and Africa. There are several confirmed cases in the United States, including one in Nassau County, in patients who had recently traveled to those affected areas.

The Centers for Disease Control and Prevention issued a travel warning to anyone heading to those regions.

There is no vaccine to prevent against the virus, and there is no cure.

Doctors say their biggest concern is a spike in a neurological disorder that results in babies being born with abnormally small heads. Officials in El Salvador, Colombia and Brazil have even suggested women stop getting pregnant until the crisis passes.

Dr. Sunil Sood, a pediatric infectious disease specialist from Northwell Health, says the carrier mosquitoes tend to be very aggressive.

"What we call daytime biters, not only at dusk and evening, and you just don't know how prevalent they are at the property where you are staying," says Sood.